Dental unit



'n n n3 INVENTOR ATTORNEY.

vJuly 28, 1931. c. w. MOORE DENTAL UNIT Filed Nov. ,6, 1928 5 Sheets-Sheet l CLARENCE. W. MOORE.

BY M M M July 2s, 1931.

C. W. MOORE v DENTAL UNIT Filed Nov. 6, 1928 5 sheets-'sheet Y 2 ATTORNEY.

July 28, 1931'. C. w. MOORE [1,815,953

DENTAL UNIT Filed Nov. 6, 1928 5 sheetssheet s si Wx I i. INVENToR.

ATTORNEY.

CLARENCE w. MOORE. Y

July 2s, 1931. C, w, MOORE 1,815,953

DENTAL UNIT Filed Nov. 6, .1928 5 Sheets-Sheet 4 AINVENTOR. l 'CLARENCE W. MOO-FUE.A

A TTORNEY.

C. W. MOORE DENTAL UNIT July 28, 1931.

Filed Nov. e. 192s 5 sheets-sheet 5 INVENTOR. CLARENCE w. MooRE,

ATToRNEY.

fio

ATENT orf-Fics WA entrain/venia, assieme "we escasa si risers,

somos' necessaria. ross f o eruit@ A Applicatiif.financieras@o, 1,928; serial mi, 317,540.

'This imei-itionrelates'to d'entalfunits,VVK y. 'Amongtheobjects ofthe invention are;y to improve'the construction otdentalv units to provide in kdentalifunit'mean's for positively 5 looking the instrument cordjsfin an 'extended position ;4 togpfrovide an improved'tensionfcon? trolling `device for dental units'y suchthatthe 'j iin'st-rurlnerrtv cordsg are "relieved of v tension f during@ the useofthe instruinentv regardless ofthe yvelocity with which the cord is vvithdrawn: froinftheu-nit'; tox improve the tension controlling inechanisinfodental units Where? by thetension onfthe cords jis automatically and 'positively relieved `When the 'cord is fully i-eallyajpplies the tensiontothekcord infresponse f to actuation "of jthei cord' y itself; to

i simplify and reduce the cost of the retrieving mechanism of" dental units ,Sto providein a bracket table dental'unitfiniprovedmeans for Supporting and'e'udihs the'nstmen and cords; toL provide in a dental unitpineans permittingquick and simple replacement of' the instrument cords; torende'ra'morecompactV assembly ot instruments in a dentalunit; and inanyother obj e'ct'sfandy advantages as Will'b'e moreapparent as theldescriptioniproceeds.:

This invention, vWhile .in certain aspects, 0f

general application, constitutes 'in'. SS'Vrful re'- i pontodout further that certain"lvrrtsrl S of plate removed toV disclose the arrangements .'W-ithinthe brackettable, y'and,showing the cord housing and guiding-channels 'in dotted k `lines-in the holl'ovvfarrnfof the bracket-table,

{jFfigfQ representsaaside elevation of'v the y i ysaine,partially-brokenlavvay,to disclose tease tures of theinvei`1tion,fjY;Y j l extended frointhe unit and'vvhich antoniatl bhsinveuton pertaeyto 'other tirrrls,0f dem I `nthe accompanying drawingglforining a part of this specification; -4 n p plan of' a bracket tabl'ei'instr-urnent `'afssei:'nl ol'y,V vvitlithe 'cover Fig; 31 represents afragfmentary enlarged planof the bracket table according toithis in,- vention, f f j same, butV partially in section, withthe instru:V mentl guldesshowvn in their extended posiytionrelative the cas-ng of thebracket table,

in dotted? lines, and showing the tension regu; latingory controlling elements in, therv-sec-n Fig. r 4a yrepresents aside elevation ofthe enttypeof dental 'unitbroken swayl to show thev application ofi the tension conia-rolling;y

latch 'of this invention, ,f

6 and Eig. represent enlarged de:

tail elevations of' the tension controlling latch mechanism and theretriever meehanlsnio 'the dental' unit shown `in Fig,

' vFigj represents a verticaly section through thearm of' the bracket table dental ins/trie: ment assembliyshown in Fig, 1, disclosingthe improved trough or channel construction therein, Y f g'Fig. Qfrepresents ka fragmentary side eleva: ,tiono'a modified forni of retrieving` device forth@ unit, n f f Fig. ,'10 represents a top plan oa modified formel? tension controlling latch mechanism according to the invention,

, FigL 1l represents a top plan oi? the pref Il y cords and. instruments of the dental Y n ferred formjofrl tension controlling taten I IFigs. 12* to lfZ-j, inclusive, y -represent 'diga grammatically' the successive positions oi tflie'latcliA pin relative the `tension controlling inthe art,`had certain disadvantages which are" eliminated by this invention! For instance,'1n the Russell constructioma point fof Wear and thus of Vpossible troubleexisted mechanism according to theinvention, and y 'latch meehanisrnin its Vcycle of movements; The bracket table instrument n assembly shown in the Russellyjpatent previously noted,

in the retrieving;l `mechanism whereby theine.

strument cords were pulled back into the easing ateruse bythe operator Eorthis i purpose Russell used a. y@loC/l5fsprigng actuy Y atdidnim with a' tare et wenn@ l the retrieving device.

the drum and connected with the sheave of -ject to breakage, as was the spring, andrequired replacement sometimes'. In the instant invention althoughit is contemplated that la rclock-spring drum may beV usedras shown inFig. 9,"yet the drum is improved to allow winding of a wire rope or cable thereon- `The Russell rconstruction l was sometimes vineffective in operation owing-to the precise movement of the instrument'cord essential to latching the'drumv against unwinding according to the pawl arrangement of that pattern. If care-was not-used'inV extending the instrument and cord from thev unit,y the pawlmight not seat, Ithe tension f would :remain and the cord would unexpectl edly be returned into the unitI with anupsetting effect upon the patient'and operator; To effect 'a positive latch, regardless ofthe velocity with whichv the cord isv extended, the invention herein'isdirected.- This phase of the, inventionfistof coursesusceptible to j wider rangesofapplication, inasmuch Vras Vthe same principle,and-construction can be- 'applied' to other types of dental units, 'asparticularly shown in Figs.l 5, 6v andA 7, and as will be pointed out further herein. The

Russell construction, moreover,` provided a rather involved construction of channel members for receivingand guidingthe. Acords and .the retrievingl mechanism, which erendered it difficult toV change the cords-inthe -t event of failure or wear, and thisxinvention simplifies that construction and enablesquick and easy replacement of the cords asl will ybe pointed out. 'The Russell bracket table instrument assembly included among its features the'mounting of the improved ksube tachment.

attachment be of the simplest nature, par-l ticularly as regards'the wiring. In the past Vthe Russell construction has involved a casunit upon a main pedestal ofjthe dental unit,

and which was arranged for subsequent-at- To this end it is desirable that ing of the bracket table soY full of instru- `ments,switches, cords, guides, and such, that it'fhas not been feasible to dispose the trans- -former for the -low voltage instruments'in 1 thecasing itself, but this has, inthe past, been disposed in-.thepedestal of; the dental Vunit, or at some otherremote position,l such that it has required a multiple cable extend-A ing from-thev instruments Vingthe casing to the V` transformer, complicating Vthe wiring and'nfecessitating skill in effecting .theV attachment of the sub-unit of thebracket table Y with the main unit;` The invention Shereinso simplifies the constructionas to enable the ldispositionk of the transformer for theinstruments inthe casing with Vthe instruments,

thus providing for the extension of ordinary vh igh voltage, (house and oiiice lighting cur-v rent) kinto the casing as the only wiring emerging therefrom, with all of vthe trans- The tape was sub-k -for pivotally supporting the arm, `and which ishollow to house conductorsextending intothe arm and casing. The hollow armV 2l receives and yhouses a plurality of troughs or guides or channels 23, as shown'in Figs. 2 and 8, andwhich are preferably formed of upper and lower stampings 24 and 25vrespeCtiVely, rigidly held in` spaced relation by a vertical web 2.6, riveted or welded tothe parallel, spaced trough members or stampings. ,The stampings have identical and Vopposite grooves or channels, the opposite pairs of which define the channelsor grooves in which a particular instrument-.cord vand its sheave will lie and move, as will bei clear,

especially in view of Fig. f8. Y t

The stampings and web extend from the arm into the casing forwardly, and rearwardly through the arm to a point spaced from the end of the arm. 21, where thexstampings terminate while the web is carried on rearwardly to bolted or riveted connection .with the arm plug 27,slidablydisposed 'in the end of the arm 21. The simplicity of the channel construction vrof thislinvention relative the original Russell-construction will be apparent. The channel assembly as a rigid unit is slidablydisposed'v in the hollow arm 2l. At the forward end, in the casing, they web 26 ter- Vminatesjust beyond the jointure of the arm and casing, while the channel stampings arecar'ried on further `into the casing, toward the front edge thereof but terminating appreeiably short thereof. i

Although it will be obvious that the channel construction of the bracket table instru"- .ment assembly may be as lshown in the Russell patented construction, and the same number soY Vof instruments may be usedv as in that construction, yet itihas been found 'thatfby providing "improved V`and 'interchangeable instruments the-number of instrument handles and cords normally necessary' forhfree and Y Vproper use of the dental unit may be reduced to four, namely two electric.v instruments,

using small cords, obviously, andone air instrument using air solely, and* one airand v electric instrument, ora total of four instruments.l The disposition ofthe channels in Vthe arm, as shown in Fig. 8, may be such Vas to place the air instruments at theouter edges, and with the smaller electric cords for the electric `instruments in the center, which vas shown provides ample y'clearance .between the i lower surface of the channel membersand the atoms the 'honte ma 1er-misuse sach renergy `conductors as necessaryL is showny Fig, l, the ehannelconstruc? Yf'ti'on and theinstrume'nt guide'and holder are such as isindicated at 2 of such V`Coinpactness that thereis adequate n space yto, receive and; house transformer, Afsthe; transform Bryconnections, ands Y y 110; bearing upon the ifi'i'stant` invention, they v ,have beenV omitted fromg-'thej disclosure y as; far

asdetailsare concernedf@ Y yAs noted, the web'c'26terrninates just 'inside f ofthe; casing between the channel 'starnpliigs,

as Aat,:30,'leaving -a clear vspace between; the channelinembers from; the `end; of the web to the end of the st-anipingsn` This spacel is toy receiveY certain movable-elements of the Strumentassembly, including Ethe improved tension; regulating .encontro-lling latch mechanism ,of this invention,vand isthe'preterred formofconstruction: `v1f. -f 1' The outerfsurfacefof. the casing is provided withlan aperture' 29fdiametrically opposite. *they connection of the lhollow yarniwith the i casing,-sothat the aperturefis in substantialV registrywith the ,hollow arm 21. f.lhe openng-29 is closed or covered byadrawerf front 31, rigidly'connectedlto aslide, or vdrimer bottom 32, extending substantially;paralleljwith theylower surfaceoffthe casing and 'suitably guided and Vsuppertedras'to' be slidably pulled through the aperture orgopening 29to expose theA instruments andperm'it'their i-ivithdra'waly fromthe casing. 'The 'rear-end of the drawer slide 32 preferably extends into the'space between the upper and lowerstanipings for the chalnnel members, in spaced relation tothe end 30 of the web joining the; stampings,in its normalclosedandheusedfposition-` if Q. The plate 32 carriestoward its rear'endthe transverse, inclined Y depressor 33, rarranged to guide the connectors orfcordsintotheir respective channel-s inthev stampings inthe hollow armv 21, as welly Yas yinto, the n' movable i guides to be described'. They transverse bar l 1 has no positive action,but simply serves as an'abutmentwith which the cordscontact.y

"if yAdjacent thel depressoror Vbarf33, on the vplate 32, toward the front thereof, are a pair f of spaced transverseelevated;platesi3l,-op-' c positely slotted toreceiveand hold rigidly i ferred thatithe pladtesl bearrangedfin pairs,

although, as shown infFig. l0, asingle plate maybe `usedy Vfor each instrument and its cord. c,

EachpairI of plates ismaintained in ,spaced parallel relation to'ad'jacent pairs; in a hatter'y: assembly, and fthefindividual plateslare separated-by 'a'space 39y which is coeXtensive Y withfaA vertical plane passing through the ap proximate center olfthey respective channels -oztlthestampings infthe' hollow'arnr21.-

Each plate of a'pair-issl'ott'ed andubent as lateris'ldescrib'ed to` cooperate with its mate ini effecting ymecha:nisinz:suitable tor controlclr mechanisms havey ling the tension ofthe cord on the instrument bysuccessive pulls on the instrument.. Each paircoinprises a] gudesurface 36, ra pri-k mary stop recess 37, a latch recess 38, a sec-y ondaryfstop recess 40, and a guide channel or slotll terminating' in the respective plates 42.r kilt; will be observed that owing to the direction of the flare on the respective plates that-the clearance between the flanges eii'ects r an enlargementiofthe space 39 between the plates 35. It will be understood that a pair of latch plates in the preferred form, will be provided for each instrument and cord jused in the unit. It will be understood that the elevated plates 34 supporting the pairs of latch plates 35, will be rigidly mounted on yjust beyond oppositely i'ared inclined flanges sof' thedrawer plate 32 as by means ospaced vertical studs 19 mounted'on plate32.

- In the Russell construction previously noted, the instruments were slidably mounted 4in individually pivoted holders, and so i y i arranged that oscillating the holder tripped or actuated a switclicontrolling the circuit through, the particular instrument.,y It. is

90.kry

contemplated that such construction may be f used in connection with theme'chanisrn heretofore; described, if desired.y lny the interest-s of compactness and simplicity, however, it is preferred that the instrument .holder `to be described will be used.

n yVertical studs 43 areprovidedon each side ofthe-sliding element v32, connected to the Y drawer vfront 31, and spaced by the end of the channelineinbers. `To thestuds a guide ears 4,5. They guide castinghas,preferably,

twocentral openings 46 and '4:7 respectively,

slidably receiving and holding'electrical in- E struments of which the handles yonly arey shown in Figs, 1 yand 3, as at 46 and47re- ,i

spectively. The guide casting is provided 0n each side'of the central openings with airy instrument receptors, such as an opening48 for the hot air syringe, and a sleeve 50 for the cut-oil for the spray bottles ofthe unit. Although the several openings in the preferably extended v guide casting yare through the casting, they are not arranged in parallelism, but converge on theinner side vof the casting, and diverge onpthe side to-` ward the drawer front so that when brought to operativeposition they are in suoli spaced relation as to permit the ready grasp of the instrument by the fingers. 'It will be understood that the airy instrument receptors, 48' and 50 Vare arranged `to receive, removably, the appropriate air instruments 48 and 50,r as disclosed. In the normal housed position y,the instruments are arranged. in substantialiio ly a 'horizontal plane parallely with the plate 32," with they endsfof the instruments well below the upper edge of theldoor front 3l. y Inf order to placethe instruments in position for y thel operator to grasp a desired instrument 1er y .y Y,

i' ikz Casting 44 is pivotally attached by ,means of f f 65' of the Russell construction, or a modification means :are Vprovided `for yswingingrthe guide casting'and the instruments with it, upward ly; This may be accomplished by the mechanismdisclosed in Figs. 3 and 4, vby the provision of a laterally extending roller 51 mounted Von the guide casting or instrument holder, in such position as to impinge upon a stationary inclined track 52 rigidlyV mounted in thecasing. lt will be clear that as .the drawer or slide is movedthrough the aperture '29, the roller 51 will ride up on the track 52,l swinging the yguide casting upon its .horizontal aXis and elevating the fan shaped battery of instruments to proper grasping position; lt is to be noted that the roller 51 is normally spaced from the track 52 to a degree sul'licient to insure that thc ends of the instruments are` beyond the ca ing edge, before moving them upwardly.

Connecting the several instruments with sources of energy',A are a plurality of cords or connectors, such as 53. The connectorsV are well known inthe art, and may comprise` electric connectors, air connectors, or a ycombinationof both. Each cord 53 is attachedin a well known mannertothe inner end of an appropriate instrument. ln the disclo' sureOf'Fig. 4, the cord passes out of the rear endA of the guide casting, the opening of which -is at ajslightly higher level than the klower stamping or channel'level, extending under the transverse-depressor bar, and vlies i in its appropriate channel. yToward the rear end of the hollow arm 21 the cord 53 j passes .about a sheave or roller 54, and passes `then toward the casing in the upper groove or channel of the stampings to a convenient point in the vcasing where itis anchored or fastened in such manner as to forni a per-y manent terminal for leads extending to a transformer, or switches or rheostats, such as are common inthe art. ln this form described, the anchorage for the cord is Vat the topand the cord is withdrawn with the in 'i struinent from the'bottoin; It is contemplated that the disposition of the cords and their attachment to the leads maybe as vdisclosed V'in the Russell patent, with the instrument and cord extended from the upper level, and

jthe anchorage for the cord at a lowerlevel, o

` convenient position for such electrical and lother connections as may be desired for the .particular instrument. lt will be clear that as in the Russell construction, the sheave 54 is of such diameter that with the cord in position the sheave is guided forward and backward in yits vproper channel during the Voperation of the dental unit. f

Vln order to retrieve the cord and instru-V Vment sothat the instrument enters the instrument holder'or guide casting duringthe non-use ofl the appropriate instrument ten- Y, sion devices are provided.

The tension device maybe the same as that thereof as shown in Fig. 9, to be later described.Vv A further modification as shown in Figs. 5, 6 and 7 utilizing the. force of gravity is also contemplated,vas willralso be furlther described.

Vor control.' yThus a latch arm `57 pivoted freely on the aXis ofthe'sheave at 58, has an inturned ange towhich the other end of the coil spring 56 is attached, with oneend of the spring attached tothe arm plug at a lower level than i'the plane of the horizontal axis of the sh'eave. The latchfarmV extends in parallelism witlithe side of the sheave for a distance past the edgeof the'sheave', where it is bent inwardly as lat 61,V and the 'free end 62Y eXtends'toward thelatch plates inthe casing. The free end 62 is of such thickness as'to pass readily into the space 39 between the plates of a pair of latch vplates 35, and is maintained in `constant registry with this space.

Thefree end 62 of the latch arm carries a transverse latch pin 63 of a length greater Y than the width of an vassembled pair of latch plates 35, but less than the widthl of the space 39 where it is enlargedV owing to the oppositely flared flanges of the plates of the pair. The latch pin 62 is resiliently maintained in a plane of travelsuch as to normally present the latch pin tothe latch plates at a level higher than the levelvof the axis 58 of the l sheave, but lower than the level of the secondary stop recess 40 of the latch plates 35. This may be achieved by lowering the plug end of the spring, or by bending the latch arm 57, as will be evident. j Y

It will be understoodthat there will be a separate retrieving mechanism for each cord and instrument, asl there are also separate tension controlling devices yfor each.

' 1n the :operation ofthe parts 'so far described, with the parts disclosed in Figs. l, 2 and 3, as well as in full lines in Fig. 4, the first step is to slide out the drawer, tothe position shown in'dott'ed lines in Fig. 4.V As the'plate 32, of the drawer, carries with itthe transverse depress'or bar 33, theV latch plates 35, and the pivotal supports for the guide casting,; these all move forward together 'f intenta:

are'incvedforwardalso(y It willfbe undeiei'` stood that suitablejlatching mechanism'for maintaining the vdrawer infopenpositionwill vbe provided. As the opening continues,'t he Q roller 51 f impinges against inclined' track k52, thus swinging the instrument holder? and the instruments to apositionlfor the operator to Y drawn atanyrate of-speed desired, and scon-y tinued until a positive stop'is had tothe outnv wardfmovement, rwhen the cordis .released andthe tension control removes the Vtension fromfthecord,thusenabling the y*operator to f graspa 'desired,instrumenti.k

Y. Theisecond step'comprisesv aiselection of an instrument thus exposed fand grasping same manually and pulling Ait from theguide cast! ing or holder.. This instrument may be withf use'lthe instrument. vAsk fthe instrument is yso ' .of therftransverse'latch' pinrai'sesthe free"y pulled outofthe casing,1dragging they attachedcord-with itfthe sheave is rotated and ypulled forward jwith the cord, 'against'the tension lofthe coil spring, and thelatch arm, of course,is moved forward rwith the sheave. Continued outward movement causes the free end ottheflatcharm to` enter the space k39,V 'between'the appropriate pair of latch plates 85', thenresulting iny the impingement of the latch'jpin` Y 63 upon the 'upwardlyfy inclined? guidesuraces 8610i?k the latch plates.k Thel pin 163 begins to vrisefonthe guide' surfaces as the/outward orfwithdrawing movement is continuedas indicated in Fig.12`. Elevation f fitfendstofmaintainthenormal horizontal positi'onin'giofothey latc'hvpin on the latch' arm.`

ont resistanceof1th`e'tension spring' 56, 'which Continuation' ofltheT vpull l causes the pin to L traveliovertheupper end of theguide surface 14.9`r ofthe-latch platesandto enter theslot ormfingfthe' severallrecessesf-atfthe entrance toy slotll. lThe'resilientimpulse ofthev pin '63 c is" downward as -soonoas Ythefrestrainingand"` guiding surface y36 is passed, which coupled wi-ththe withdrawing pull onfth'e 'instrument causeg-"qthepin to abut-fV and `be""po'sitively Y I further movementjbeing ,positively stopped', o 55andthis ylimitation` occurslre'gardless ofthe Y ,stoppedby-seating in the primary stop recess' 37 The primary and secondary stop recesses are separated` by adwell or point 59, prevent-` ingthey pnjfrom passing directly'irom one to the other vertically'. f'fThis marks the termination ofy the outward pull onthe instrument,

speedof the withdrawal@ The, instrument is then released rby the operatonbut the 1transv. verse-pin moving rearwardlyand downward-V ly "under `the influeiicejoi` the tension 'device f1 passes into positive vstopping relation' to the 1v l'atchrecess 38 in thelatchplates," The ten#y Vfsiorronfthe sheaveis thusl takenv directly byy *i thcflatchplates, and removediromfthe cord. v The operatorfis'fthen freey to use the'iristr'u-` Y ment without `danger fof l its sudden, with#Vr drawal lfrom' 'his grasp. 1 4The' use' ottheinl,

strument being concluded, the operator gives?k the* instrumentl a little `tu g outwardly,`moving therflatch pin outifrom itsseat inthe latch ,recess,iand1,'under the resilient influencel of the tension;k spring, limoving itvforwardly and downwardly into the 'secondary stop recess/l0,

ei'ect'ing a furtherpositivestop to Vits out-y ward movement. *Release loi the 'instrument atv-thisspoinuthe tension of the coil spring nowlhaving attachedrto the ycord again, and: still under the downward influence of the tenL` sion spring,`the pin 63 passes into the slot 41,!

in which it isrgui'ded bythe inclination ofthe slot, downwardly; As the pin moves inthe f f slot the continued downward movement ofthe pin causes it to passfrom a position where 'the resilient influence is downward,fthrough" its position of normal rest, to a klower level where the resilient inlluencefisupward, so

kthat bythe time it reaches the end of the slot 41, the Limpulse isupward so that the pin, and

the armfto which it is attached uponrelease` from the slot, by passing into the larger 'area yof the space 39 between the plates, eil'ectedby the outward flare of the flanges,'42,springs'y upwardly as 1 the sheave moves rearwardly," completely released from engagement withf `the latch plates; y Qi w The cycle 0i' operations just described will be clear, "it is believed, *but the several positions are indicated in theFigsjlQ to 17 inclusive. ZlnFig.' 12,' the pinffha's just begunto move vupwardl-y on the guide surfacesl ofthe latch plates. In Fig. 13 it' has passed intof ftheiprimary stop'recess. [In Fig. 14,itha`s' seated Vin. the latchy recess. ,In Fig'. 15itV hasj seatedinV the secondary stop recess,inFifg.

e 16y it hasy starteditspassage through thexslot'- 41, and' iniFig. 17 it has reached theend of the slot, and in'dotted lines, has sprung `upwardly y'free of the'latchplates. i

In' the retrieving mechanism--sliown'in Fig.

pivoted 'to' it',l asin the preferred "form, but

.the rear'end'thereoi' has a cableGl connected to' it' This cable is vwound!upon a-spring 'actu-p y yateddrum, rotatably mounted on af's'haft`- 66. --'The'cablefislofsuch diameter as topermit kseveral turns to lie against the periphery of tlie'ldrum before winding upon ritself on the .drum Thedevices and mechanisms for efj fectin'g tension4 on' the instrument cord areA manifestly of wide range,'and'it `is to, be vvun-vjy n derstocd that all suchare contemplated in' A connection with the .other portions of the in vention herein set forth.y

1 There isA well known 'type'. of dental unit; in` .which the instruments, instead j of being mounted inV a horizontally extending casing, are Vsup'ported on a vertical pedestal with thef cords for the instruments dependingfwithin o thel pedestal. Suchiadental unit is-disclosed. in Fig. 5, and the retrieving device of-- th isimitl Y isla `guided weight maintaining the'tension on 136 the vcord througli`tlie-`-`force of gravity. The

ico f pedestal 67 has for each instrumentapair of spaced vertically extending -guide rods i 68, (Fig. 7 'upon Which a sheaveY journal 70 is slidably mounted. The wsheavejournal may have va depending Weight (iQ-*and rotatably supports ka sheavey 71, about yWhichan instru- "ment cord y72 is passed, anchoredV at one end relative Ythe pedestahior attachment of lead` connections, etc., and at the other attached to an instrument 7 3. Pivoted to one cheek or leg Y of the `journal 70, as at 74, is a latch arm 75,

.15' travel bya tension spring ,77 Y Y of travel ofY the latch arm 7 5, so that upwardV It will be understood that the operation of the tension controlling mechanism in the dental unit disclosed in Figs. 5, 6 and 7 Will be the same as inthe other types disclosed. It

may be noted, also, that' the provisionsoi aseparate device for maintaining the resilient positioning of the transverse latch pin, apart Vfrom the retrieving tension device', as shown .in Figs. 5, 6 and 7, is in contemplation With regard to the disclosed, I

. The many advantages of the improvements preferred form of dental unit eliectedherein'wilhi it is thought, be apparent,

I Yas Will the :tact-that the modifications availli able are. of Wide range, and such are to be con# 1 strued'as Within the scopevof the invention.V

' There is anadditional .factor of advantage fected byl extending or withdrawing the at tached instrument `to its greatest jextent, and locking the latch arinto the tension regiilat-` ing latch plates, as Will be cl-ear. `The forward vT cluded by a stop 78, :mountedon the casing that .should be 'brought out',` namely, the ease and facility With which new co'rds may be inv serted and yattached to the .instruments and the r-etrieving devices.

and52, the changent any desired cord is efmovement. of the channel members or stampings withV the-cords and instruments is preand abutted by the edge of a; channel stamp-e ing.l With the retriever in close association Withvthe latch plates, which have beenmoved forward' with the sliding drawer bottom, the

entire channel and Web assembly is slid end- Wise out of the arm, moving the end plug, or arm-plugvvith it, and exposing the desired sheave over or from Which the old cord :may be Aslipped laterally, on its free side opposite to the latch arm, and the nevvone replaced.

Thef attachment of theV cord to the anchorpoint in the casingand tothe instrument may be' quicklyeiected While thesheave is locked to the 'latchplate's In order to support thef channelmembers inproper Vvertically posif tioned relation, alrectangular guide support is fprovided'at therear of the casing", With.

in which the channel stampings 4are guided, as Willbefcle'ar.y Y 'Y y 'I claim: f

lfIn agdental-unit, an 'energy conductingv cord, means imparting tension to the cord, an.,

element movable ina single fixed predetermined path in response to movement ofrsaid cord, stop means disposed in the path of. said elementl arranged to be abutted by said element to positively limit the movement of; said cord, and means arranged to absorbl the' tension on said cord subsequent to the'stopping,abutment.v Y'

2.1111 a :dental iunit, ank energy ,conducting cord, means imparting tensionito Ysaid cord,

means `posit'ively-'operable ata predetermined Y point in the movcinentof the cordl to stop the movement of said cord, and means-operj able subsequent to the operation of the-stop means to absorb the tension on vsaid cord.

, 8. Ina dental unit a OuideV Val cord eXzteiifA sible through the guide, 'retrieving machanism tending to pull `the cord in one direction i lrelative the guide, avlatch element movablek With the retrieving mechanism ina single fixedpredetermined path, tension controlling means disposed in said pathpin proximity'tothe guiderarranged forpositiveinteren-gagement With the 'latch element toward thel end ofthe opposite movement. of the cord throughthe guidato absorb the pull of the retrieving.

mechanism on saidcord. t. In a vdental unit, alongitudinally guided cord and retrievingmechanism, cooperating n latch elements respectivelypivot-ally mountedV on the retrieving mechanism and fixedinthe path koi movement of the other 'cooperating latch elemen t,arranged for intereng-agement and releasing disengagement in response to,` pulls onl vthe cord 'opposed to the; retrieving mechanism'. 1 l.

v 5., Tension controlling mechanism forre trievers-of dental units, including a lslotted and recessed plate, and an arm having a cross, pin, ,thel arm and plate susceptible to'relativev longitudinal movement in response to .anti-v retriever pull and arranged forfrelative latev `eral movt-:ment for interlocking 'and disengagement of the crosslpin and the slots and-. Y recesses, Yalso in .response to anti-retriever;

pull;

- V6, in connecting the instrument with a sourceY of energy, a retrieving mechanism including ya Vsheave and means imparting apull 'on-thea'dental unit, an instrument, av cord l Sheave, tension controlling mechanismV in-J Y cluding a'movable' arm,}a latching element mounted on thefarnu the 'arm arranged for movement with the retriever, means .tending resilientlytov maintain thev arm in-aprede,v termined position, lthe tension@.controllingVIV mechanisin.' including` latch `ine'chanijsm dis-l Y posed jin the pathfjof travel of 'the latching -Y y' estates f mechanism* for rl`serially yint'eilo'clriirig andjdis- -engaging theflatclr .element and; the;` latch mechanism through ifmove-mentsrv ofz the y arm "under, the influenceofthe resilient means, for

f relieving-tension onztheicord during the use, ofthe instrumentmf 7 f." Inga rdental 'unitincluding cords and instruments, y means for' housingf: the i cords randinstruments, means for holding the 1n';

ystru'ments in a substantially horizontal comf mon plane in their housed position, means' responsive `to the .last vnamed movementV to` yactuate the instrument holder and simultanemovable to expose the instruments, and means ,ously yextend all of` the instruments at ank e 'angleto the horizontalgto lfacilitate grasping the instruments. Y

-8. Ina dentalunit,'ahoiusing having a subvstantially'horizontal planar yupper surface,"

an instrument holder they yaxis of which normally liesfin substantialparallelism with said upper surface, an instrument` normally mounted in said `lholder, means movabletoy f expose the instrument, and means synchronf ously actuated by the movable means to move the instrument holder so, ythat its axis is y plane 'of the upper f surface/of the housing;-

j h e 1 f9 In a dental, unit including ay plurality` of;l instruments, an yinstrument'holder for lsupportinga'y plurality "of instruments, a

angularly inclined to the housing for the instruments, means `for mov- Ving*theinstfrl'im'ent holdery and instruments yfrom .therhousing, "and means actuated said' movementlto swing the instrument holder at anangle' to theiline of movement'of said irstmentioned' means. i y

1l).A In 'avdental .unit including instruments y and cords -connectingwith sources of energy, a'housing for thecordsandinstruments, a

' niymfable` instrument holderpresenting the *holder relativeqasaid means to facilitate instruments iny a substantially fan shaped assembly, means for-moving the instrument vholder and instrumentsrelative thek housing,

and simultaneously moving the" instrument grasping an instrument. p y f 1 1. Ina dental unit a plurality of sub-y fstantially rkparallel *closely grouped j cord guides, a purality of instruments,` a horizon-y tally ypivotally lsupported "instrument holder yhaving instrument apertures4 the axesVV of which converge inwardlyso'as'to terminate in "substantial alignment with the respective' cordV guides, the'instruments removably Y mounted :in therespective apertures and out- /fanshape to facilitate graspingan instru, se

emony substantially horizontalplane and ar#` ward'ly `divergent therefrom in substantial ment, and eachgnormally disposed in a com'- .ranged for movement-as.. a unit ,with the holdersol as tolliein a common plane anguf larly i divergent yf ,from` 'and intersecting the horizontal;

' element on i* said l arm', means on nthe "latch i l2.r` In a ,dental `1`nita hollow arm, a casing carried by ythe arm, a unitary guide channel i u slidablymounted yin the arm and extending -v Ainto thecasing, the guide channel including a vertical web terminating short o'f the channel'mem'bersv in the casing, an arm pluggcarf ried yby the; guide channel, loopedy cords and sheaves disposed'in the channel members, af movable'element carried by the casing and extensible vinto and from the space, between gagementwith the sheaves to facilitate re-v ,75 #the channel members beyond the termination f the web and arranged for interlockingen-kr placement of the cords,- and supplemental i guide members carriedby saidmovable ele-- ment.

sof Y 13. dental unit, a housing, an instru` Y ment, a cord connecting the `instrument with a source4 of energy and being looped, ar sheavef disposed mftheloop, tension means for the? sheave, fa iresiliently held: arm pivotally'; as-r l lso'ciatedwith the sheave so as toy beinovablef n therewith, with the arm resiliently urged toa predetermined position, andineans in they, path of movement of ysaid arm for locking7 engagement therewith to; absorb the tension. y

on the sheaveand to relievethe cordfr'omy tension during theuse of the instrument.l

la. In akdental unit, a'latch plate havingk primary and secondarystop recesses, and a' rbeing relatively thefdental unit.y .i

Y ,15.A In a'dental unit, a housing, raninstru#k mentgcord guide, cord extended into ythe rguide andlooped in the housing, kretrieving mechanism engaging the'loopedcord urging itsfmovement Vone way through thejguide, a

movable element supporting the guide, a ten-A sion controlling device mounted on the movable element, means carried with the retrievA-VVV ing mechanism in apredetermmed path such yas toimpinge Kupon the tension controlling device, the movable element arranged toe):-

the loop, an armpivoted o-n they axis of theV sheave, a tensiony device engaging said arm iesf f" andimparting tension to the sheave for re i trievingthe cord, means in the pathyo'f said i armduring thenormal movement of the cord for engagement with the arm for effecting av f positive stoprtothe outward movement ofv the' cord, said means and arm arranged for latch-4` inginterengagement upon release of the cord," Y f to relieve thecord of tension yfrom the tension' las I i lio 'f pose orconceal `the cord guide, the cordar^ Vranged to be extended' through the guide to cause Acontact between said means and the ten-' [sion controllingdevice, andthe latter ar- M `ranged" to y serially interlock and disengage said means to relieve vandimpart tension to reis device, 'and the'means andarrn arranged Yfor disengagement vupon further outward pull on said cordto permit the ycord to behoused. f Y

A1-7.- l:In.afdenta-l unit, a housing, guide channels mounted'in Vthe housing including a web' terminating short of one endofthe channels, amovable element'carried'by the housing eX- T tendedinto'the 'space between the Channels,

a battery of latch plateslcarried ontlie mov` able kelement and normally disposedv in saidspace between the channels,.a pivoted instru- 'ment holder carried bythe movable member or element, instrument cords extending from movable"elementv being Varranged so as to be extensible partially trom the housing solas to expose the :'instrumentholder, means re'- sponsive tooutward movement of the element to expose such instruments as are carried thereby, the Vbattery of latch platesV being movable With the elementto a position clear of thecliannel members, means movable in a ,predetermined path between the .channel members with thecord as it is extended fromV the housing arranged to engage and latch iWith thev appropriate latch plates at the outer limit' of the Vmovement of the cord, and means effecting upon the disengagementvof said means and the lappropriate latch plates to retrieve the cord andvdispose it in the housing.

18. AIn a dental'unit, a pair or' oppositely rffiaredparailel spaced'latch' plates, each latch plate having identical gui-de surfaces, prii maryand secondary stop recesses, .anda latch recess, and each Vhavingalsovaslot inclined ltherein communicatingivvith the secondary' stop recess and terminating substantially be# i yondtheflare, a cooperating resiliently pivot clined slot during relative longitudinal movements of the arm and latch plates.` Y

said path Aand'located substantially between the cord guide and the retrieving mechanism and arranged for positive 'interengagement With the Vlatchelenient atlapiredetermincd point in the movement VVof said `vcofd lin one direction, to absorb the puller1 the retrieving mechanism ofsaid cord.

- Intestimony whereof, I ailix my signature.'

CLARENCE lV. MOORE.'

the instrument holderv into the channels the .toi-swing the instrument 'holder on its pivot -V y' icc Y 19. In a dental unit, an energy conducting cord, an element movable in a predetermined substantially rectilinear path in responseto movement of said cord, means disposed in alinementwith thefrectilinear path of movement fof said element and arranged for positive locking engagement therewith at a` pre-V `Y determined point in the movement otsaid `cord to absorb the tension'on said cord.

20. In a ydental unit, a cord guide, la cord'Y 'extensible through the cord guide, retrieving mechanism tending toY pull the cord in oneV direction relative to the cord guide, a1 latch element, a substantially' rectilinear guide with' Y relation to which the latch element is mov-Y able'inf response to movement ofthe cord in a predetermined substantiallyvf rectilinear "path,l tension controlling means disposed in Y 

